Comparison of stellar hydrodynamic codes
R. Andrassy and the Code Comparison Collaboration
Heidelberg Institute for Theoretical Studies (presenting author)
Motivated by the scarcity of verification and validation efforts with the 2D and 3D hydrodynamic codes currently used by the community studying the hydrodynamics of stellar interiors, we have decided to compare the outputs of several major codes used in this field. Code verification is typically done by solving a simple problem and comparing the code's output with a known (semi-)analytical solution. We use a problem that does not have any known exact solution but is directly relevant to the current discussion in the field: turbulent convection and convective mass entrainment from a stably stratified layer. The purpose of this study is to provide the community with estimates of code-to-code spread in quantities such as the convective mass entrainment rate, power spectra of the turbulent convection, velocity profiles, fluxes of enthalpy and kinetic energy, or dissipation rates. We already have test runs performed using the codes FLASH, MUSIC, PROMPI, and SLH and partial implementations in the codes CASTRO, MAESTROex, and xRAGE. The codes differ in the discretisation of the Euler equations, time stepping methods and, in the case of MAESTROex, a low-Mach approximation to the Euler equations is used. Most of the implementations have been done by scientists actively using and developing these codes for their own research. I will report on the status of the project and first results on behalf of our collaboration.